The present invention relates to processing of modulated signals, including frequency-modulated signals such as Bluetooth signals. More particularly, this invention relates to processing of modulated signals that includes processing to alter the modulation index of such signals.
Various signaling or communication systems require modulated signals with particular modulation characteristics. For instance, the Bluetooth specification requires the use of a Gaussian frequency shift keyed (“GFSK”) modulation format with a modulation index, m, that is between 0.28 and 0.35. The performance of a demodulator may depend on the characteristics of the signal it demodulates. For instance, demodulators exist that have good performance with frequency shift keyed (“FSK”) signals that are nearly orthogonal, i.e., that have a modulation index of about 1. The performance of such demodulators can be lower when demodulating signals with a different modulation index, such as the lower modulation index signals required by the Bluetooth standard.